This application is based on applications No.HEI11-146992 and HEI10-197156 filed in Japan, the content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an information recording/displaying card. More particularly, it relates to an information recording/displaying card comprising an invisible information recording part and a visible information display part in which information can be written in under predetermined heating conditions and written information can be erased, and an information recording/displaying system using the card.
2. Description of the Related Art
In accordance with a recent increase of interest in saving and recycling resources, recording media such as paper are desired to be repeatedly used. In attempts to develop techniques for this purpose, rewritable thermosensible recording materials in which data can be recorded and erased by using heating means such as a thermal head are regarded as promising. Such reversible thermosensible recording materials have various applications and can be used for the purpose of not only recycling recording media but also visualizing information recorded in an IC card, a magnetic card, or an optical card. card.
As conventional reversible thermosensible materials, a leuco dye/developer-subtracter, an organic low molecular weight/high molecular weight resin matrix and a polymer cholesteric liquid crystal are known.
The color of a leuco dye/developer-subtracter is exhibited by opening a lactone ring included in the molecules of the leuco dye and erased by closing the ring. The lactone ring can be opened when the temperature is increased and then rapidly decreased, and can be closed when the increased temperature is gradually decreased. The leuco dye/developer-subtracter is coated on a sheet material, so that data can be written by using a thermal head and can be erased by allowing the sheet to pass through heat rollers.
A known organic low molecular weight/high molecular weight resin matrix includes BA (behenic acid) as an organic low molecular weight compound and PVCA (copolymer of vinyl chloride and vinyl acetate) as a high molecular weight compound. This material can be switched between a transparent state and a scattering state in accordance with a heating temperature, and the switched state can be retained after cooling. This material is coated on a sheet material, so that data can be written in by using a thermal head.
As a polymer cholesteric liquid crystal, one obtained by polymerizing a vinyl compound including a cholesteric liquid crystal compound in a side chain is known. When this material is heated to a temperature exceeding the crystallization temperature and then rapidly cooled, a display color can be changed and fixed.
In using the leuco dye/developer-subtracter, the display color depends upon the leuco dye, and hence, full color display of an arbitrary image cannot be obtained. In using the organic low molecular weight/high molecular weight resin matrix, an image is displayed by using the transparent and scattering states, and hence, full color display cannot be obtained. In using the polymer cholesteric liquid crystal, the display color can be changed in accordance with a heating temperature on principle. However, the change of colors takes a time on the order of minutes, which is a large obstacle to putting this material into practical use.
In view of the aforementioned disadvantages, an object of the present invention is providing an information recording/displaying card and an information recording/displaying system using the card in which invisible information can be recorded and displayed as visible information and visible information can be written and erased as color images in a practical amount of time.
In order to achieve the object, the information recording/displaying card of the present invention comprises a visible information display part and an invisible information recording part. These parts are disposed on the front and back surfaces of the card, respectively or arranged side by side on the front or back surface of the card. The visible information display part includes, as a main component, a low molecular weight cholesteric liquid crystal compound having an isotropic phase transition temperature higher than a melting point, and information can be displayed, written once and erased therein. The invisible information recording part is, for example, a magnetic recording layer, a write-once optical recording layer or an IC (integrated circuit) memory, in which information can be recorded and erased.
The information recording/displaying system of this invention comprises information erasing means for erasing information recorded in the visible information display part of the information recording/displaying card, and recording means for recording information in the invisible information recording part.